I have to be honest - I've looked and looked and looked at this, and unless you had photos taken from exactly the same point in space of two airplanes, one with and one without the 4% l/e extension, in exactly identical lighting conditions, I don't think you can really see it.

You are probably right, but when I compared the old Revell DC-8 wing with the much newer Minicraft kit wing the difference is very clear.

It is not all about the accuracy, I actually find it fascinating to research these idiosyncrasies - all part of the hobby I guess.

Shame we have no DC-8 here in the UK to crawl over.

I did capture a number of pics at Manston a few years ago of the old MK -55F before she was cut up - non really capture the leading edge. Shame this machine has disappeared as she had a significant earlier life with SAS & KLM.